Alpha-amylases (alpha-1,4-glucan-4-glucanohydrolases, E.C. 3.2.1.1) constitute a group of enzymes, which catalyze the hydrolysis of starch and other linear and branched 1,4-glucosidic oligo- and polysaccharides.
There is a long history of industrial use of alpha-amylases in several known applications such as detergent, baking, brewing, starch liquefaction and saccharification, e.g., in the production of high fructose syrups or ethanol. These and other applications utilize alpha-amylases derived from microorganisms, in particular bacterial alpha-amylases.
One of the first bacterial alpha-amylases to be used was an alpha-amylase from B. licheniformis, also known as Termamyl™, which has been extensively characterized and the crystal structure has been determined for this enzyme. Alkaline amylases, such as the alpha-amylase derived from Bacillus sp. strains NCIB 12289, NCIB 12512, NCIB 12513, and DSM 9375 (disclosed in WO 95/26397), form a particular group of alpha-amylases that are useful in detergents. Many of these known bacterial amylases have been modified in order to improve their functionality in a particular application.
Termamyl™ and many highly efficient alpha-amylases require calcium for activity. The crystal structure of Termamyl™ shows that three calcium atoms are bound to the alpha-amylase structure coordinated by negatively charged amino acid residues. This requirement for calcium is a disadvantage in applications where strong chelating compounds are present, such as in detergents or during ethanol production from whole grains, where the plant material comprises a large amount of natural chelators such as phytate.
Calcium-insensitive amylases are known, e.g., the alpha-amylases disclosed in EP 1022334 and WO 03/083054, and a Bacillus circulans alpha-amylase having the sequence disclosed in UNIPROT:Q03657.
It would therefore be beneficial to provide alpha-amylases with reduced calcium sensitivity.